The present invention relates to a lens-fitted photographic film package having a package body which is previously loaded with a photographic film and in which simple exposure mechanisms are incorporated. The lens-fitted photographic film package is hereinafter called simply a film package. The present invention relates especially to such a film package for stereoscopic photography.
Stereoscopic photography takes advantage of parallax and convergence of the optical axes of the left and right eyes for making a photographic image which appears as if it were three-dimensional. As a stereo camera for taking such stereoscopic photography, for example, a Nimslo stereo camera with four lenses (trademarked "NIMSLO 3D") is known. In the Nimslo stereo camera, four taking lenses are disposed horizontally side by side at a given distance from each other in the front of the camera body, and four picture frames are recorded simultaneously in the area corresponding to two full-size frames, whereby the four picture frames of a same subject are each approximately half of a 35 mm film frame in size, and have a uniform parallax relative to each other according to the given distance between the taking lenses. That is, a subject is taken from four slightly different points of view during each exposure. By printing a set of four picture frames on a photographic paper provided with a transparent lenticular sheet, such as is disclosed in U.S. Pat. No. 3,751,258, and by using four printing lenses which are optically equivalent to the four taking lenses of the stereo camera, a stereoscopic photograph is produced.
The above-described conventional four-lens type stereoscopic camera is large in size and expensive, because four picture frames are to be taken simultaneously in an area corresponding to two 35 mm full-size frames with the use of a specific exposure mechanism.
On the other hand, film packages are known worldwide which are previously loaded with a film and have simple exposure mechanisms such as a taking lens, a shutter, a film advancing mechanism and the like. The film package is a kind of single-use throwaway camera that makes it possible to take pictures at will without buying or carrying about an expensive and heavy camera. A single-use disposable camera must be cheap and light, so the film package must also be simple and compact in construction so as to minimize the cost and the weight thereof. For this reason, a single-element taking lens is incorporated in the film package.
Recently, the resolving power of taking lens and photographic film has been so remarkably improved that such a large (half-size) negative is not always necessary for printing a stereoscopic photograph of popular size (76 mm.times. 12 mm to 83 mm.times.114 mm). Therefore, it may be possible and reasonable to provide a single-use film package that can take stereoscopic photographs. For this purpose, it is proposed to record two or three picture frames of small size, e.g. 12 mm.times.18 mm, within an area corresponding to a 35 mm full-size frame.
However, in order to record small size frames in such a way, specific members such as specific exposure chambers for forming corresponding exposure light paths and exposure frames are necessary, which will increase the cost of the device. In addition to this, such small size frames can increase dead spaces in the film package. Not only is the provision of a plurality of taking lenses and a complex exposure mechanism for a stereoscopic camera disadvantageous from a standpoint of cost and size of the film package, but also the occurrence of dead spaces worsens the problem.
Because film packages of the type described use a single-element lens as the taking lens for lowering the cost, it is necessary to prevent picture images from being affected by the distortion that is inevitable when an optical image formed by a single-element lens is projected on a flat surface. To compensate for this distortion, conventional film packages are so constructed that the film surface is gently concavely curved in the exposure position.
Also in a stereo camera, it will be understood that a plurality of single-element taking lenses disposed horizontally side by side like the above-described Nimslo camera will form a plurality of images having different distortions if the film surface is planar. If a set of images taken at once by a stereo camera have different distortions, since the parallax among those images is variable, it is impossible to make a stereophotography by printing the set of images onto a photographic paper in the form of a lenticular sheet.